Google engineers deny Chrome hack exploited browser's code

Several Google security engineers have countered claims that a French security company found a vulnerability in Chrome that could let attackers hijack Windows PCs running the company's browser.

Instead, those engineers said the bug Vupen exploited to hack Chrome was in Adobe's Flash, which Google has bundled with the browser for over a year.

Google's official position, however, has not changed since Monday, when Vupen announced it had successfully hacked Chrome by sidestepping not only the browser's built-in "sandbox" but also by evading Windows 7's integrated anti-exploit technologies.

"The investigation is ongoing because Vupen is not sharing any details with us," a Google spokesman said today via email.

But others who work for Google were certain that at least one of the flaws Vupen exploited was in Flash's code, not Chrome's.

"As usual, security journalists don't bother to fact check," said Tavis Ormandy, a Google security engineer, in a tweet earlier today. "Vupen misunderstood how sandboxing worked in Chrome, and only had a Flash bug."

"It's a legit pwn, but if it requires Flash, it's not a Chrome pwn," tweeted Chris Evans, a Google security engineer and Chrome team lead, using the security-speak term for compromising an application or computer.

Justin Schuh, whose LinkedIn account also identifies him as a Google security engineer, chimed in with, "No one is saying it's not a legit exploit. The point is that it's not the exploit [Vupen] claimed."

When asked to confirm the source of the vulnerabilities it exploited, Vupen was blunt in its refusal to share any information.

"We will not help Google in finding the vulnerabilities," said Chaouki Bekrar, Vupen's CEO and head of research, in an email reply to questions. "Nobody knows how we bypassed Google Chrome's sandbox except us and our customers, and any claim is a pure speculation."

Last year, Vupen changed its vulnerability disclosure policies when it announced it would no longer report bugs to vendors -- as do many researchers -- but instead would reveal its work only to paying customers.

"When it comes to critical vulnerabilities, all software vendors/devs (including Google) always try to downplay the findings," Bekrar said on Twitter.

"I was thinking something similar about researchers who inflate their accomplishments," Schuh replied, also on Twitter, to Bekrar.

The point made by Ormandy, Evans and Schuh was that Vupen didn't exploit a bug in Chrome's own code, but in Flash, which has been partially sandboxed in the stable version of the browser since early March 2011.

While the Google engineers seemed to acknowledge that a bug in Flash was involved in Vupen's exploit, they also defended the sandbox technology -- meant to isolate Flash from the rest of the computer -- even as it apparently failed to prevent an attack.

"The Flash sandbox blog post went to pains to call it an initial step," said Evans. "It protects some stuff, more to come. Flash sandbox [does not equal] Chrome sandbox."

The blog Evans referred to was published in December 2010, where Schuh and another Google developer, Carlos Pizano said, "While we've laid a tremendous amount of groundwork in this initial sandbox, there's still more work to be done."

Chrome's Flash sandbox is currently available only in the Windows version of the browser; Google has promised to implement it in the Mac and Linux editions, but has not yet done so.

While Bekrar later hinted that Vupen's exploit did leverage a Flash vulnerability, he said the attack code also took advantage of at least one other bug. "[Chrome's] built-in plug-ins such as Flash are launched inside the sandbox which was created by Google, so finding and exploiting a Flash or a WebKit vulnerability will fall inside the sandboxes and will not circumvent it," he wrote. "A sandbox bypass exploit is still required."

Chrome has a reputation as a secure browser, in large part because of its sandbox technology. Chrome is the only browser to have escaped unscathed at the last three Pwn2Own hacking contests, the annual challenge hosted by the CanSecWest conference in Vancouver, British Columbia, and sponsored by HP TippingPoint's bug bounty program.

In March 2011, no one took on Chrome at Pwn2Own, even though Google had offered a $20,000 prize to the first researcher who hacked the browser and its sandbox.

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